Phosphate recovery by crystallization has been a concern in recent years. However, to obtain a high efficiency in crystallization, the phosphate concentration in the influent stream is an important factor to control. This study aims at the fractionation and concentration of phosphate from synthetic water in novel electrodialysis (selectrodialysis) to increase the concentration/purity as a pretreatment prior to crystallization in a pellet reactor. The stack consists of three anion exchange membranes, three monovalent selective anion exchange membranes and four cation exchange membranes (Fig.1). The selectrodialysis performance under various current densities (46.9, 62.5 A.m-2), and pH values (8, 10, 12) was discussed. It was found that the higher the pH of the product stream, the higher the phosphate concentration can be. The concentration of phosphate in the feed stream decreased from 3 to 1.1 mM and in the product stream it increased from 0 to 5.4 mM in 6 hours of batch mode run with pH=8 and current density of 46.9 A.m-2, while with pH=12, the concentration of phosphate was 6.4 mM in the product and 1.1 mM in the feed stream, respectively. The results also indicate that at the same pH, with a lower current a higher final concentration of phosphate in the product stream is obtained. Therefore, this study proves that the novel electrodialysis stack is feasible and effective to fractionate phosphates from monovalent ions in the mixture.  

Evaluation of a novel electrodialysis process for phosphate fractionation in wastewater

246th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.